1. Field of the Invention
The present invention relates to an air bag device for vehicles and, more particularly, to an air bag device which inflates an air bag installed in a vehicle upon collision of the vehicle to protect a passenger.
2. Description of Related Art
One air bag device, proposed by JP-U-58-23756, inflates an air bag installed in a vehicle upon collision of the vehicle to protect a passenger. The air bag in the air bag device is inflated toward the passenger along the inside of a windshield from an upper side of an instrumental panel. However, as concerns this type of air bag device, the air bag is rapidly inflated the toward the passenger by means of kinetic energy produced by gas which rapidly flows into the air bag from an inflator (gas producing means). In order to solve this problem, a dual bag type air bag device is proposed by JP-A-5-262195. This air bag device includes a container, including an inflator, fixed in front of a passenger seat, a main bag folded in the container, and an inner bag including holes therein for allowing to flow gas therefrom and folded in the container. In this air bag device, when the gas produced by the inflator upon collision of the vehicle flows into the inner bag, the inner bag is inflated. After that, the gas flows up and down in the main bag through the holes formed in the inner bag, and the main bag is inflated toward an area in front of the passenger seat.
The dual bag type air bag device can decrease inflation speed of the main bag compared to a single type air bag device which does not include the inner bag because in the dual bag type air bag device the gas dispersively flows into the main bag through the holes formed on the inner bag. Though the inflation speed is decreased by holes formed on the inner bag, it is not sufficiently decreased because the inflation speed depends on gas pressure in the inner bag, thus, the passenger may receive an impact from the air bag.
Further, according to the air bag device proposed by JP-A 5-262195, when the upper half of the passenger's body is suddenly inclined forward upon collision of the vehicle, the edge of the main bag is inflated earlier than the upper part of the main bag, and then, the main bag is inflated upward. Thus, the passenger' head inclines forward after the edge of the main bag contact with the passenger's body, and the passenger's head is thrusted up, as a result, the passenger may receive an impact from the air bag.